Glass compositions



3,485,646 GLASS COMPOSITIONS Albert E. Junge, New Kensington, Pa., assignor to PPG Industries, Inc., Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed Oct. 21, 1965, Ser. No. 500,229 Int. Cl. C03c 3/16, 3/30 US. Cl. 10647 6 Claims ABSTRACT OF THE DISCLOSURE The present invention relations to ultraphosphate glass compositions of high durability and low temperature melt.- ing characteristics. The invention particularly relates to phosphate glasses of the following composition:

Comp onent: Percent P 55-80 BaO -30 CaO 2-6 PbO 3-7 Li O 0.5-2.0 A1 0 0-1.0

Various phosphate glass compositions have been developed which exhibit relatively good chemical durability. One such family of phosphate glasses is disclosed in US. Patent 2,577,627 issued to Alexis Pincus, Dec. 4, 1951. The glasses disclosed consist essentially of the low atomic weight metal metaphosphates. The glasses are said to be very resistant to attack by fluoride vapors and hydrofluoric acid.

US. Patent 2,077,481 issued to Paul Huppert and Hans Wolff, Ludwigshafen-on-the-Rhine, Apr. 20, 1937, discloses a family of phosphate glass compositions having high ultraviolet light transmission characteristics and good resistance to solarization effects. The increased resistance to solarization is attributed to the use of ammonium phosphate as a batch ingredient. A typical glass is produced by fusing 5.4 parts aluminum oxide, 4.3 parts magnesium oxide, 13.5 parts barium carbonate, 148.4 parts secondary ammonium phosphate and 30.6 parts nitric acid at a temperature of about 1200 C. (2192 R). All parts are parts by weight. The calculated chemical composition is 5.4 percent A1 0 4.3 percent MgO, 10.5 percent BaO, and 79.8 percent P 0 All percents are given in percent by weight.

US. Patent 2,441,853 issued to John E. Stanworth, May 18, 1948, discloses a family of soft phosphate glasses exhibiting what is called good chemical durability and which have high coefficients of thermal expansion. A high coefficient of thermal expansion is desired because these glasses are intended to be used as seals to copper metal. The compositional area of this family of sealing glasses is defined by the following ranges of the oxide ingredients, listed in percent by Weight: 28 to 38 percent P O 8 to 24 percent A1 0 0 to percent B 0 15 to percent PbO, and 10 to 20 percent Na O plus K 0. The preferable B 0 range is 5 to 15 percent.

US. Patent 2,294,844 issued to Frederick Gelstharp, Sept. 1, 1942, relates to phosphate glass batch compositions containing no free phosphoric acid. These phosphate glasses are used to produce optical lenses. The glass batches claimed contain to 100 percent by weight aluminum metaphosphate, 0 to 26 percent by weight of nited States Patent 0 "ice an alkali metal monophosphate and from 0 to 27 percent by Weight of monomagnesium phosphate.

US. Patent 3,149,234 issued to H. P. Hood et al., Sept. 15, 1964, relates to a family of very soft, high density phosphate glasses for use in high energy radiation shielding windows. The claimed family of glass compositions contain about 26 to 51 percent P 0 33 to 56 percent water and a total of 12 to 26 percent of an oxide selected from the group consisting of PhD, HgO, and A1 0 all percents being on a mole percent basis. Various other optional glass forming oxides can be incorporated in these glasses in amounts not to exceed about 5 mole percent. These optional oxides are A1 0 BaO, Cs O, K 0, SnO and ZnO. These glasses are subject to attack by atmospheric moisture and must be protected during use.

What has been discovered in the present invention is a family of ultraphosphate glass compositions exhibiting good chemical durability and which can be melted at relatively low temperatures. The glasses are particularly suited for use in multilaminar radiation shielding windows and for fabricating many types of glass specialty products.

The calculated compositional ranges of the various oxide ingredients of the glasses of the present invention are presented below. All percents are given in percent by weight.

Component: Percent P 0 55-80 BaO 15-30 CaO 2-6 PbO 3-7 Li O 05-2 A1 0 0-1.0

As indicated above, the glasses of the present invention are ultraphosphates. The definition of an ultraphosphate glass is one which contains a concentration of phosphate in excess of the phosphate concentration present in a metaphosphate compound.

Phosphoric acid (HP O contains three hydrogen ions each having a valence of +1. Substituting a metal ion such as aluminum ion having a valence of +3 for the hydrogen content produces aluminum orthophosphate (AlPO Metal metaphosphates are produced by first removing a water molecule (1-1 0) from phosphoric acid (H PO leaving HPO and then substituting a metal for the remaining hydrogen content. The substitution of aluminum for the hydrogen content of HPO for example, results in Al(PO or aluminum metaphosphate.

The glass compositions of the present invention contain still a higher concentration of phosphate than is contained in the metaphosphate compound, giving rise to the term ultraphosphate.

The characteristics of the glasses of the present invention are unusual because earlier investigators concluded that glasses containing concentrations of P 0 in excess of the metaphosphate proportion (ultraphosphate) were highly water soluble. The ultraphosphate glass compositions of the present invention disprove this conclusion.

The ultraphosphate glasses of the present invention are particularly suited for use in radiation shielding windows. One of the most troublesome problems associated with multilaminar radiation shielding Windows is that during irradiation the glass sheet of the laminant closest to the source of radiation sustains a considerable build-up of electrical charge. If this build-up of electrical charge be- 3 comes too great, spontaneous fracture of the glass sheet occurs.

Another problem associated with radiation shielding windows is that most glasses tend to color upon being irradiated with high energy radiations. This induced coloration is undesirable because it reduces visibility through the windows. Both spontaneous fracture and radiation induced coloration are minimized using the glasses of the present invention. In addition, if the degree of radiation induced coloration in the windows becomes objectionable, it can be removed by a low temperature heat treatment.

The glasses of the present invention can also be used to fabricate many other types of glass articles in addition to radiation shielding windows due to their low temperature melting and forming characteristics. The glasses can be used, for example, to fabricate (1) stained glass artwork products, (2) as a base for various fiber glass-glass matrix composites, (3) as the matrix glass for machinable glass flake-glass matrix composites and (4) as a low temperature castable glass to produce articles, such as inkwells, book ends and ash trays.

These glasses are particularly attractive to the small volume glass fabricator producing a wide variety of different colored products since colorants can be added without altering the desirable melting and forming characteristics. Typical colorants suitable for use with these glasses are compounds containing iron, chromium, manganese, nickel, cobalt, selenium, copper, silver and gold. These colorant compounds can be present in the glass in amounts up to about 0.1 percent by weight based on the total weight of the glass.

The present invention will be more fully understood by making reference to the following detailed examples.

Example I is the preferred embodiment of the present invention and is the best mode contemplated by the inventor for practicing the teachings of his invention.

EXAMPLE I A preferred composition of the present invention (Composition A) is presented below. All percents are percents by weight.

COMPOSITION A This preferred glass composition was prepared by mixing the following raw batch materials in the amounts indicated in an 800 milliliter Pyrex beaker. The batch indicated produces about 325 grams of glass.

4 COMPOSITION A BATCH Batch material: Weight in grams Phosphoric acid H PO 340.0 Barium oxide 72.0 Lead oxide 16.0 Calcium oxide 12.0

Lithium carbonate 10.0

Aluminum oxide 0.4

The phosphoric acid was placed in the Pyrex beaker first. The other batch materials were then added. The

0 batch was then thoroughly mixed by stirring with a Pyrex stirring rod.

The beaker was then placed on a wire screen support and slowl heated to a temperature of about 932 F. over a period of 1 hour using a Bunsen Burner. The temperature was then raised to 1400 F. and held there for an additional 1 /2 hours. The temperature of the melt was then reduced to 1200 F. for an additional /2 hour. The beaker was then removed from the burner and the molten glass poured onto a steel plate to form a glass patty approximately 4 of an inch thick by about 6 inches in diameter. When the glass patty had cooled to about 400 F., it was placed in an oven at a tempertaure of about 400 F. The power to the oven was then turned off and the glass was slowly allowed to cool to room temperature over a period of about 2 hours to anneal the glass. The glass patty thus prepared was water clear and of good optical quality. The specific gravity of the glass was determined to be about 2.95 grams per cubic centimeter and exhibited an index of refraction of about 1.547.

To compare the chemical durability of Composition A with several other glass compositions, the following three tests were conducted. The glass durability samples used in the tests were 2 inches long by 2 inches wide by about A of an inch thick.

TEST I Test I consisted of boiling the glass sample in water for 1 hour.

TEST II Test II consisted of boiling the sample in a /2 percent by weight sulfuric acid aqueous solution for 1 hour.

TEST III Test III consisted of boiling the sample in a /2 percent by weight sodium hydroxide aqueous solution for 1 hour.

The calculated chemical compositions of the glasses compared for chemical durability are presented below in Table I. All percents are given in percent by weight.

TABLE I I II III IV V U.S. 3,149,234, U.S. 2,077,481, U.S. 2,441,853,

Radiat on Ultraviolet Durable-high Compo- Plate shielding transmitting thermal expansition glass glass sion glass .1

The results of the three chemical durability tests on the glass compositions investigated are presented below in Table 11:

TABLE II.DURABILITY TEST RESULTS These three glasses were then subjected to the three chemical durability tests described in Example I. The results are presented below in Table III.

Weight loss in milligrams per 5 TABLE III o gl a s s i i riaiia Weight loss in milligrams per hour per square centimeter Softening Test I Test II Ifit IIII of glass surface (Water) ('Acld) ka 1) Softening Test 1 TestII Test 111 G1 355 N0: point, F. (Water) (Acid) (Alkali) 1) 2 2 2 Glass composltion' 1 678 0. 11 a. 29 2e. 05 1, as; 0.13 0.0 4.90 668 0 U 3 75 1 sec 0. 3s 26. 26 4 90.6 66 34 Composition A 675 0. l 4. 1 11. 4 5 0- 1 The softening point could rottbe tigtgminedtusingtarllldard tetclli 15 niques because the glass was es roye y IHOlS me a ac rom e atmosphere. EXAMPLE 1H 9 'ififilly destroyed. d d 3 ass serious y amage 4 Glass severely damaged. Samples of glass composltions A, B, C and D were prepared by melting the batch materials and then casting the These durablhty testimdlcafi? that composltlon A of molten glass on a steel mold in accordance with the the present lnvention is relatively durable compared procedure described in Example L the P y known Phosphate based glass The cast slabs were then ground and polished to the tions. Composition A is not as durable as the commercial desired fi ti soda-lime-silica P1ate glass COmPOSIUOH tested Various measurements were then made on these glass position III but t s the advantage 0f being melted and samples to determine their suitability for radiation shieldformed at much lower temperatures. ing windows. The results are presented below in Table IV.

1 TABLE IV Visible transmission Visible transmission Visible transin percent of in percent of Dens1ty Log of mission in incident light after incident light after in grams electr cal percent of 1X107 rads at 1X107 rads and after per cubic conductrvrincident light room temperature 1% hrs. heating at centimeter ty at 20 C. (Unirradiated) (75 F.) 120 0.

Composition:

A 2. 954 13. 1 91. 5 26. 1 90. 5 3. 010 13. 1 91. a 24. 5 as. 9 2. 912 13. 1 so. 6 21. 1 as. 0 2. 915 14. a 90. 4 21.0 88. 6

EXAMPLE H The ultraphosphate glass compositions of the present invention are umque in that certam of the radiation m- The fOHOWIIIg Yaw batch mateflals 9 glass fP duced color can be bleached out by raising the temperations B, n D f the present mention were s ture of the glass to about 120" 0. By maintaining the out and converted f glasses In accordance Wlth the glass temperature at about 120 C. during irradiation, the P fif Presented 111 Example I used to Prepare glass remains fairly clear. The commercial glass compos1t1on A. positions used in the fabrication of radiation shielding windows do not have the ability to be appreciably bleached Welght m grams by heat treatments as low as 120 C. Com osi- Composi- Composi- The glasses of the present invention are also highly Batch mammals C twnD resistant to spontaneous fracture because their electrical Phosphoric acid (85% n roi 546.4 579.6 454.0 conductivities are approximately 10 ohm centimeters ggg gf 3%;? 25:8 51? compared to conventional radiation shielding glass com- ICJalcium OX i% 6: .t igg positions which have electrical conductivities of approxith'um car ona e. 15 Aiunnnum oxide 0. a 0. 56 0.36 mately 10 ohm centlmeters- 60 Although the present invention has been described in terms of specific examples, the invention is not so limited. The calculated chemlcal cDmPOsmOns of gl The invention should only be limited by the language of C, and D are presented below. The compositions are the appended claims given in percent by weight. I claim;

1. An ultraphosphate glass consisting essentially of in Percent by Weight percent by weight 55 to 80 percent P 0 15 to 30 per- Compo- Compo- Oomp cent BaO, 2 t0 percent C30, 3 t0 7 percent PbO, 9.5 srtion B sition c sition D to 2.0 percent L1 0, and 0.0 to 1.0 percent A1 0 havmg a softening point between 650 F. and 700 F. 62.8 64.7 7 2. An ultraphosphate glass according to claim 1 which 2:3 2:2 2:: contains up to about 0.1 percent by weight of a metal 1.7 1 colorant compound, the metal of the colorant compound 1% being selected from the group consisting of iron, cobalt, 1 100 0 100 0 selenium, copper, silver, gold, chromium, manganese,

nickel, and mixtures thereof.

3. An ultraphosphate glass consisting essentially of in percent by weight 68 percent P 0 22 percent BaO, 4 percent CaO, 5 percent PhD, and 1 percent U 0.

4. An ultraphosphate glass consisting essentially of in percent by weight 62.8 percent P 0 25.2 percent BaO, 6.0 percent CaO, 4.7 percent PbO, 1.2 percent Li O, and 0.1 percent A1 0 5. An ultraphosphate glass consisting essentially of in percent by weight 64.7 percent P 0 25.0 percent BaO,

5.1 percent CaO, 4.1 percent PbO, 1.0 percent Li O, and 10 0.1 percent A1 0 6. An ultraphosphate glass consisting essentially of in 8 percent by weight 71.1 percent P 0 19.5 percent BaO, 4.4 percent CaO, 3.6 percent PbO, 1.3 percent Li O, and 0.1 percent A1 0 References Cited UNITED STATES PATENTS 2,920,972 1/ 1960 Godron 10647 FOREIGN PATENTS 728,808 4/ 1955 Great Britain.

JAMES E. POER, Primary Examiner 

